When is a Headache More Than Just a Headache?

While medical schools usually teach headache under the heading of neurology, headache is actually one of the most common complaints in primary care offices. As a result, the primary care doctor must be able to differentiate a headache that requires symptomatic treatment from a headache that is a symptom of a more severe underlying condition. Headache, or cephalalgia, is defined as diffuse head pain that does not fall within the distribution of a nerve, and is experienced by 95% of the population at one time or another.[1] Over half of the world population can be diagnosed with a primary headache disorder, the three most common being tension-type headaches (~38%),[2] migraines (~10%),[3] and chronic daily headaches (3-5%).[4] These headaches cause severe pain and loss of productivity, which can be as much as $1.4 billion per year for migraines alone in the US,[5] but they are non-fatal conditions. While only 10% of the headaches that present fall into the category of secondary headaches, [6] the underlying medical conditions that cause them can be fatal if not recognized and treated.

The International Headache Society Classification ICHD-II categorizes secondary headaches as those headaches that can be attributed to: head and/or neck trauma, cranial/cervical vascular disorder, non-vascular intracranial disorder, substance use or withdrawal, infection, disorder of homeostasis, cranial structure abnormality, or psychiatric disorder.[7] While there is occasionally a clear context for the headache, such as recent trauma resulting in intracerebral hemorrhage or pregnancy leading to idiopathic intracranial hypertension, many conditions present more subtly with a more ambiguous time course. For example, a remote history of trauma or chiropractic neck manipulation could be the only historical clue to a subdural hematoma, arterial dissection, or dural sinus thrombosis as the cause of a patient’s headache.[8] For this reason, a focused history must also include a thorough past medical history of travel, trauma, and recent illnesses. A good history, including characterization of the pain, duration of symptoms, trigger symptoms, patient characteristics, associated symptoms, substance or medication use, and precipitating factors, is the most important part of identifying red flags that will alert the physician to an underlying organic etiology.[9] It is also important to ask the patient where the pain is located, how often it occurs, how long it lasts, what time of day the headache occurs, what improves or worsens the symptoms, and whether there are systemic symptoms such as fever, chills, nausea, and vomiting. It is also important to find out if this headache is something novel for a patient and whether the symptoms associated with the headache have remained consistent or progressed in severity over time. Sometimes severe headache is just a severe headache but a headache that worsens from mild to severe and begins to produce vomiting and a sensation of vertigo is a headache that requires further investigation.

Red flags on history suggesting an organic etiology for the pain include: short duration, headaches triggered by cough or exertion, rapid onset, age over 50 years, and a patient with HIV or cancer. Secondary headaches last 2.9 months on average, significantly less than the 8.2 month duration of the average primary headache disorder.[10] Headaches triggered by cough, Valsalva, or exertion are associated in 60% of cases with increased intracranial pressure, most often due to a hindbrain malformation or intracranial mass.[11] A description of thunderclap headache, characterized by an abrupt onset with a crescendo of pain, could result from hemorrhage into a mass or an arteriovenous malformation, arterial dissection, cerebral venous thrombosis, spontaneous intracranial hypotension, reversible cerebral vasoconstriction syndrome, pituitary apoplexy, and acute hypertensive crisis, or idiopathic primary thunderclap headache; nevertheless, subarachnoid hemorrhoid (SAH), which occurs in 11 to 25% of these presentations,[12] must be ruled out due to the 50 to 70% rate of morbidity and mortality associated with this etiology.[13] New headache in a patient over 50 years of age should also be considered as a symptom of a primary or metastatic tumor, cerebrovascular disease or giant cell arteritis, which could be ruled out with blood tests for erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), markers of inflammation. Immunocompromised patients, such as those with HIV or transplant recipients, as well as cancer patients should also be worked up for organic causes of headache such as toxoplasmosis and metastatic disease. [14] Other warning signs on history include headaches that worsen with postural changes, headaches that cause sleep awakening, and new-onset side-locked headaches, but these warning signs have lower yield predicting an underlying organic cause.[15]

While the history is often the key to diagnosis and often dictates what further work up is needed, physical exam findings also play a role in elucidating an organic etiology for headache. Papilledema is present in as many as 40% of patients with intracranial masses. [16] Similarly, these patients may also present with neurological findings, such as alterations in consciousness, pathological reflexes, hemiparesis, ataxia, alterations in sensation, or cranial nerve deficits; these neurologic findings are particularly concerning when they are focal, such as being unilateral.[17] Systemic symptoms such as fever and nuchal rigidity must be considered as possible markers for meningitis or encephalitis, and weight loss should be assessed in identifying occult malignancy.[18] These physical exam findings should also alert the physician to an organic cause of headache.

In the case of headache, imaging work up cannot be neglected if red flags are revealed on history or physical exam. If SAH is suspected, a CT scan is the best diagnostic test to rule in the diagnosis, having a 74% sensitivity up to 3 days after the bleed. If the CT scan is inconclusive and SAH cannot be excluded clinically, a lumbar puncture should be obtained to look for xanthochromia, a sign of blood products in the CSF, which persists for several weeks after a CT has lost its sensitivity.[19] If a mass lesion or a posterior fossa syndrome is suspected, an MRI should be obtained to best visualize these abnormalities.[20] Common diseases being common, most practitioners will never diagnose a brain tumor or a subarachnoid hemorrhage and rightly place primary headache disorders at the top of their differential diagnosis; nevertheless, physicians must keep secondary headaches in mind and must be vigilant in ruling out underlying medical causes of headache which if left undetected could lead to unacceptable morbidity and mortality.